The term "micro-system" refers to a component which transforms a physical magnitude into an electrical signal (i.e., a micro-sensor, for example, a micro-accelerometer or, on the other hand, which varies a physical magnitude, generally in the form of a displacement of a movable part, by application of an electrical signal (i.e., a micro-actuator, for example, a micro-pump, typically for a micro-syringe, or a micro-motor).
These components often comprise movable parts which move on the order of a micrometer ("micro-moving"), and are therefore, by their very nature, very sensitive to mechanical constraints imposed by their environment.
Thus, in the typical case of a micro-accelerometer, if the component is glued directly onto the substrate with a rigid glue of the epoxy resin type, for example, the simple mechanical constraints generated by this gluing could alter the sensitivity of the micro-sensor, reduce its capability to support overloads, or perhaps block its functionality completely.
For this reason, in the current state of the art, the direct transfer of such components onto a hybrid circuit substrate is a delicate task necessitating the utilization of flexible glue and of a silicon substance to protect the electrical connections.
A known direct transfer technique calls for first mounting the device on a chip-carrier which in turn is then mounted on the substrate, but then economy of space becomes a concern.
Even with advances in known techniques, to absorb any differences in dilation (i.e., expansion) coefficients between the material of the substrate (ceramics, glass epoxy, etc.) and that of the component (silicon, quartz, etc.), the presence of an intermediate resin is nevertheless indispensable. Typically, a first transfer of the component onto an intermediary silicon substrate (the silicon/silicon interface not presenting any such dilation coefficient related difficulty), is followed by a transfer from the intermediary substrate to the hybrid circuit substrate, which, for example, is ceramic, with interpositionning of the resin between these two substrates.